So today my friend Jeremy Brown was telling me that he is having trouble with a few spots on his shots that seem to be showing up on his shots no matter which of his 4 lenses he uses. He correctly identified that it was dirt in the camera, but didn't know what to do about it.
After discussing it with him and discovering that his Canon 20D (which is several years old) had never had a sensor cleaning, it became clear that it was time to get Jeremy educated on how to clean his sensor.
But wait, won't cleaning it ruin my camera?
Well, if you do it wrong it will certainly ruin your sensor which is the single most important part in your camera, so you should certainly take this matter seriously.
Why not just pay someone to do it?
Yeah, you can do that - for $100+, but the dirty little secret is that the people that clean it may have some college kid in the back room doing it for the first time or not taking special precautions, and in this day and age of blame the customer do you think they are going to accept liability and replace your sensor if they do it wrong?
Yeah, right! Your more likely to hear that there as a problem with your sensor and that cleaning simply uncovered that problem that you are responsible for, and it is due to wear and tear - not something you can claim under warranty. It is for this reason that many people have come to the conclusion that no one will treat your sensor with better care and take the job more seriously than you - especially when you know that doing it the wrong way will cost you big $$$.
Okay, now I'm terrified - what do I do?
Education my friend, and there's no better place to get educated than http://www.cleaningdigitalcameras.com/. After you read that outstanding article, you'll need to get your supplies. However, you'll need to know what to get first, so you can do that by finding your camera here at http://www.sensorswab.com/cameras_bymfg.html and choosing the correct swab number and solution (E2 or Eclipse). If you get this wrong then you are going to damage your camera, so be careful. Some people will use a Sensor Wand with PecPads but Photographic Solutions doesn't recommend this method. Others use brushes, etc... (all of which are discussed at http://www.cleaningdigitalcameras.com/, but the safest bet seems to be Sensor Swabs and the correct solution. Be especially careful if you have a Canon 5D as it seems there was a problem with solutions on its sensor that caused Photographic Solutions to have to shell out some warranty labor and funds to correct.
So how do I know if my sensor is dirty?
You'll first sign that your sensor is due for a cleaning when you start seeing dots like those in the picture below:
However, you can do a quick test to find out simply by getting a white sheet of paper (or opening up a all white document on your computer screen) and taking a picture at the most narrow apeture your lens supports (usually between f/22 and f/32) with your lens auto focus turned off (you don't need to focus for this test and the AF will hunt forever turning to take this shot so it is best to turn it off). When you do that you'll notice spots like the ones shown in my picture, and that is what you'll need to remember when cleaning your sensor.
Yep my sensor's dirty
Yeah, it happens to all sensors and some even come that way straight out of the box when you get them. The good news is that generally a dirty sensor isn't going to be very noticeable until you start shooting at narrow apertures like f/16 or above (pixel peepers - i'm generalizing for a broad audience here).
The important thing for you to remember is that you MUST follow the directions carefully, or else a new sensor at your expense will be in your future. NEVER use the same swap or pecpad for more than one wipe (even though those stupid swabs are $2 each and you'll need about 3 for a typical cleaning).
But my sensor is still showing a few spots when I'm done
Yeah, welcome to the nightmare of sensor cleaning. You may find it very difficult to get your sensor perfect, so that is where the dust delete data feature found in new cameras like the Canon XTi, XSi, 40D, etc... comes in REALLY handy. This feature allows you to capture dust data using a special feature on your camera much in the way you tested your sensor for dust, but it stores this data with the picture so that software that can read this data will remove those dust spots for you automagically (sometimes). The only problem with this feature is that dust moves constantly and you'll collect more when you change your lenses, so you need to capture this data frequently for the best results.
But my camera has a built-in sensor cleaner
Congrats - this is a great feature which will save you a lot of headache, but you'll eventually be cleaning your sensor like the rest of the world. The only advantage you have is that you'll do it less regularly because the built-in solutions work fairly well - but nothing is 100% (short of living in sterile, dust free room your entire life).